Stencil sheet



machine or of a stylus.

practically acetone-insoluble.

Patented Nov. 30, 1926.

UNITED STATES PATENT OFFICE.

EDWARD W. HILL, OF CHICAGO, ILLINOIS, ASSIGNOR TO A. B. DICK COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

STENCIL SHEET.

No Drawing.

This invention relates generally to typeimpressible stencil sheets suitable for use on the mimeograph or other stencil duplicating machine and particularly to that type of stencil sheet in which is employed an open porous base, such as yoshino, provided with a normally impervious coating in which characters may be formed by impact or pres sure, such as that of the type of a writing In Letters Patent No. 1,526 982, granted February 17, 1925, I have disclosed 'and claimed broadly such a stencil sheet, the coating whereof'includes a cellulose compound as, for example, a cellulose ester in a suitable solvent. The present invention concerns an embodiment of this broad idea in a form with which gzod results may be obtained in practice. The best known and most commonly used esters of cellulose are the nitrates and the acetates. It has been found that certain advantages inhere in the latter (in which I include other fatty esters or compound fatty esters of cellulose) as, for example, they are less inflammable and are non-explosive, for which reason they can be compounded more safely than the former with solvents of comparatively low infiammability. They may also be readily modified and softened to adapt them to the intended purpose. Stencil sheets of the so-called dry type, that is, not requiring moistening preliminarily to stencilizing the same, coated with suitably compounded cellulose acetate, operate well under the impact of the type and produce copies of excellent quality.

Cellulose acetate as it occurs in the mar ket or may be made in the laboratory is of several kinds and of varying solubility, but the common commercial varieties seem to fall into two distinct classes, one which is soluble in acetone and the other which is Either variety is capable of yielding stencils of commercial quality. The acetone-soluble cellulose is that which scientifically is produced by the partial saponification of the directly acetylated product or so-called triacetate, while the acetone-insoluble material consists primarily of the product directly acetylated to the triacetate. The acetone-soluble compounds are, therefore, the so-called group Application filed April 6, 1925. Serial No. 21,206.

of acetyl hydro celluloses and may so be regarded chemically, but whether the cellulose acetate be soluble or insoluble in acetone, its solutions in any volatile solvent With which I am acquainted may be modified in such a manner as to produce a satisfactory commercial stencil. Compound cellulose fatty esters, such as the nitro acetates, or esters made by the use of two or more fatty acids in union with the same ('ellulose molecule, would constitute fatty esters of cellulose which would no doubt yield colloidal homogeneous films capable of producing entirely satisfactory stencils.

In carrying out my invention, I employ, generally speaking, cellulose acetate in a suitable volatile solvent, such as acetone, a tempering agent or agents, one or more of which may be (wholly or in the main) a solvent of the cellulose acetate or may be characterized by substantial nonwolatility, in which case it will remain as a part of the coating mass. To this coating mass there is added a tempering agent and a lubricating agent. The tempering agent may have modifying properties or a distinct modifying agentmay be added in addition to a tempering agent. The tempering agent for the celluloseacetate colloid may be one of the following: the amyl and butyl tartrates and phthalates, monoacetin, triacetin and esters of gylcerin or of other polyhydric alcohols.

The substances mentioned above as tempering agents exert a solvent or gelatinizing effect on the cellulose acetate, and unite with the colloid to produce a homogeneous film. Modifiers are not solvents for the colloid but cause a homogeneous film when used with a mutual volatile solvent which is evaporated.

The lubricant added to the coating is a special type of disten'der distinguished by the fact that it has lubricating properties. The function of a distender is to extend the homogeneous film. Some distenders possess definite lubricating properties; that is, establish inter-molecular lubrication. The non-lubricating distenders include Turkey red oil, bentonite, powdered soapstone and zinc oxide. The distenders which have definite lubricating properties include chlorinated naphthalene and other hydrocarbons,

acid ester of dissolvd 5 grams of chlorinated naphthalene and.

drocarbons of the higher aromatic coal tar series and the halogen derivatives thereof. Castor oil arid zinc stearate are also lubri- .cants when used with cellulose acetate but lack this property when used with nitrocellulose.

One distinction between temperin or modifying agents on the one hand an lubricatin' and distending agents on the other,

is that t etempering and modifying agents.

are capable of forming a homogeneous, elatinous and continuous film with the co ulose acetate, while the lubricants and the distenders do not possess this property.

To the coating containing the tempering or modifying agent and the lubricant, there may also be added coloring agents such as Prussian blue. I

M invention may be practiced by the use of t e following formula, the proportions stated being approximate:

20 grams of cellulose acetate of the acetone-soluble grade are dissolved in 400 grams of ood commercial grade acetone. To this, t ere is now added a mixture consisting of 75 grams of monoacetin (the monoacetic glycerin) in which has been 8 grams of castor oil.

fThere is now added a mixture consisting 2 grams of Prussian blue in 5 grams of castor oil. v

Then there should be stirred in 10 grams of stearate of zinc and.

10 grams of Turkey red oi-l (sulfonated castor oil).

The mixture so produced will be found to be 'of about the proper consistency for a lication to sheets of yoshino paper by t e "drawing process commonly inuse. If

too stifl", however, this may be readily remedied by the addition of more solvent or oil or both. After the coating operation the sheets may be hung fora short time to permit the evaporation ofv the volatile solvent, after which they will be ready for stencilizing in the usual'manner.

.As representative of a second working formula. inwhich are used esters of the higher "alcohols :which may be regarded as more powerful 'ifying and softening agents of the c ulose acetate, the following formula may be employed:

gramsof a 10% solution of cellulose acetate in acetone. To this may be added 50 cc. of a 16% solution of starch acetate in acetone I 10 gm. castor oil 10 gm. chlorinated naphthalene 45 cc. dibutyl tartrate.

At ord' azy. temperatures this makes a 'ity of the stencil sheet for hoino may scribed.

Another com to this mass is iamyl hthalate, and it may wholly or in part-rep ace the dibutyl tartrate 'm the formula given. The acetate of starch, while not an absolutely essential constituent, nevertheless improves the qualractical purposes. Other higher alcoho s than amyl and butyl are no doubt suitable for the preparation of esters of the character of gneous'mass from which stencil sheets 7 dibutyl tartrate and diamyl phthalate and other polybasic acids than phthalic and tartaric will yield compounds which are applicable for the purpose.

The foregoing statements of preferred methods of practicing the invention are I not to be regarded as limitations with respect to scope, for it is obvious that other substances may be substituted or added and that this may necessitate variations of the proportions stated. Thus, with suitable grades of cellulose acetate, other volatile substances than acetone may be employed. Monoacetin, may be re laced wholly or in part by diacetin or trlacetin or mixtures thereof, or similar esters of glycerin and other polyhydric alcohols, such as the glycols. The chlorinated naphthalene may also be replaced by other halogenated hydrocarbons and possibly by certain hydrocar-.

bons-themselves. Castor oil, while the best product of its kind for the purpose which ias been found, need not be regarded as,

and may not be, a necessity, as other oils of similar properties such as rapeseed, olive, almond or peanut oil, may be used, in whole or in part, for the same urpose. The coloring ingredient may, 0 course, be varied widely; for example, the Prussian blue may be replaced by'lake colors or by d estufi's soluble in the mixture. Chlorina-te naphthaleneis also a lubricant in the compositions referred to. Turkey red oil (sulfonated castor oil) may be replaced by sulfonated corn oil or by sulfonated oils derived from other saturated or partially unsaturated oils. I

If desired, the coating compound as hereinbefore set forth, orthe essentials thereof,

may be combined with other ingredients to vary the character of the resultant mass forthe production of desired efl'ects. Thus there may be employed, in conjunction with the cellu ose acetate in proper solution and with other softening or tempering agent or agents, salol (phenyl salicylate), acetanilid, triphenyl or tricres 1 phosphate or other substances which wi I modify the character of the coating mass either by coagulation",

or upon the evaporation of the volatile solvent. As in the case of the formulae above specifically stated, the result will be a ion homogeneous, type-impressible, colloidal, coating substance capable of use throughout an extended period of time without moistening preliminarily to stencilizing.

It should also be pointed out that certainof the higher esters of cellulose may be solnble in a non-volatilesolvent. Where these are used. such solvent becomes a more or less permanent constituent of the coating compound which should be applied to the yoshino while at a somewhat elevated temperature -or, at least, a temperature sufficiently high to hold the cellulose ester in solution. After the coating operation the sheet may be hung for a sufficient time to attain a moisture balance, particularly Where a constituent having more or less hygroscopicity (n1onoacetin, for example) is employed. Such a iomparatively nonvolatile solvent for cellulose acetate is represented by ortlio-nitro-toluol, although be cause of its toxic properties, preference would naturally be given to another substance or other substances having the capacity of acting as a solvent of cellulose acetate. The higher alcohol esters of phthalic and tartaric acid, either alone or when mixed with other substances and used in connection with a suitable cellulose ester, may form (outing masses which can be handled in this manner.

What I claim is 1. A type-impressible stencil sheet comprising a porous base having a coating including a fatty acid ester of ccllulose,a lubricant and a tempering agent.

2. A type-impressible stencil sheet comprising a porous base having a coating including a fatty acid ester of cellulose and a halogenated hydrocarbon.

A type-impressible stencil sheet comprising a porous base having a coating including a fatty acid ester of cellulose, a

halogenated hydrocarbon and a tempering,

agent.

4. A type-impressible stencil sheet comprising a porous base having a coating including a fatty acid ester of cellulose, a halogenated hydrocarbon and castor oil.

5. A type-impressible stencil sheet comprising a porousbase having a coating including an acetone-soluble fatty acid ester of cellulose.

6. A type-impressible stencil sheet comprising a porous base having a coating including an acetone-soluble fatty acid ester of cellulose and a lubricant.

7. A type-impressible stencil sheet comprising a porous base having a coating including an acetone-soluble fatty acid ester of cellulose and a tempering agent.

8. A t vpe-impressible stencil sheet comprising a porous base having a coating including an acetone-soluble fatty' acid ester of cellulose, a lubricant and a tempering agent.

9. A type-impressible stencil sheet comprising a porous base having a coating including a fattyacid ester of cellulose and a higher-alcohol ester of a polybasic acid.

10. A type-impressible stencil sheet comprising a porous base having a coating including cellulose acetate and a higher alco- 'hol ester of a polybasic acid.

prising a porous base having a coating,

including cellulose acetate, starch acetate and diamyl phthalate.

16. A type-impressible stencil sheet comprising a porous base having a coating including cellulose acetate, a higher alcohol ester of a polybasic acid and a lubricant.

17. A type-impressible stencil sheet comprising a porous base having a coating including cellulose acetate, an acetate of starch, dibutyl tartrate and castor oil.

18. A type-impressible stencil sheet comprising a porous base having a coating including cellulose acetate, an acetate of starch, diamyl phthalate and castor oil.

19. A type-impressible stencil sheet comprising a loose fibred base provided with a coating of glycerol fatty acid ester, phthalic acid ester, and a binding agent.

20. A type-impressible stencil sheet comprising a porous base having a coating including cellulose acetate dissolved in acetone, phthalic acid ester, butyl tartrate, and a lubricant.

'21. A stencil sheet comprising a porous base having a coating including cellulose oleaiginouspla'stif ing, stabilizing and sof tening. a ents to orm therewith a homoge-.

neous in -proof body which may be readil stenciled by the types of a typewriter.

tening agents form therewith ahomoge- I neous ink-proof body which may be readily stenciled by the types of a t ewriter. the homogeneous body also including a lubricating agent;

This specification signed this 30th day of March, 1925.

EDWARD HILL. 

